Taxonomic diversity masks leaf vein–climate relationships: lessons from herbarium collections across a latitudinal rainfall gradient in West Africa

Figures & data

Figure 1. Minor vein architecture of representative specimens with low (A,B) and high vein densities (C,D). (A) Pentadesma butyracea, (B) Drypetes gilgiana, (C) Stereospermum kunthianum, (D) Ziziphus mucronata. Bar = 500 μm (all at same magnification).

Figure 2. Relationships of vein density (VLA, major VLA, minor VLA) with leaf area, and of VLA, 1° diameter, and leaf area with MAP based on PGLS.

Table 1. Trait–trait and trait–climate relationships of the whole data-set. r, correlation coefficient as determined with PGLS. VLA, total vein density; LA, leaf area; Diam, diameter (of vein order 1°–3°); MAT, mean annual temperature; TS, coefficient of temperature seasonality; MAP, mean annual precipitation; PS, precipitation seasonality; p, probability; df, degree of freedom.

Trait pair	r	p	df
VLA - LA	−0.20**	0.002	234
major VLA - LA	−0.52***	< 0.001	234
minor VLA - LA	−0.05	0.40	234
Diam 1° - LA	0.70***	< 0.001	233
Diam 2° - LA	0.65***	< 0.001	232
Diam 3° - LA	0.37***	< 0.001	215
VLA - MAT	0.02	0.79	236
VLA - TS	0.13*	0.045	236
VLA - MAP	−0.10	0.11	236
VLA - PS	0.13	0.055	236
major VLA-MAT	0.08	0.19	236
major VLA-TS	0.14*	0.03	236
major VLA-MAP	−0.10	0.12	236
major VLA-PS	−0.08	0.18	236
Diam 1°-MAT	−0.07	0.27	235
Diam 1°-MAP	0.29***	< 0.001	235
Diam 2°-MAT	0.00	0.91	234
Diam 2°-MAP	0.19**	0.004	234
LA-MAT	−0.12	0.06	234
LA-TS	−0.30***	< 0.001	234
LA-MAP	0.31***	< 0.001	234
LA-PS	−0.25***	< 0.001	234

*** p < 0.001

** p < 0.01

* p < 0.05.

Table 2. Relationships between vein traits and leaf area with climatic variables, comparing the whole dataset with subsets segregated according to family or gross venation type. Values are correlation coefficients (r) as determined with PGLS. The bottom part illustrates changes in the strength of the correlations in the subsets relative to the whole data-set (“All”). +++, increase in strength (positive or negative) ≥ 0.3; ++, 0.29–0.2; +, 0.19–0.05; 0, 0.49–0 (a decrease is given in the same way but using “–” instead). Because λ has a very low power to detect phylogenetic signal in small datasets (<25 individuals; Malvaceae, craspedodromous venation), we also present correlation coefficients for scenarios with no influence of the phylogeny (i.e. λ = 0; equivalent to ordinary least squares regression) and λ = 1 (equivalent to a pure Brownian motion model). VLA, total vein density; LA, leaf area; MAT, mean annual temperature; TS, coefficient of temperature seasonality; MAP, mean annual precipitation; PS, precipitation seasonality; N, number of individuals. Here, we distinguished craspedodromous (craspedo), brochidodromous (brochido) and eucamptodromous (eucampto) venation and additionally grouped all pinnate (i.e. non-palmate) venation types.

Traits	r
	All	Fabaceae	Combretaceae	Malvaceae		non-palmate	craspedo	brochido	eucampto
N	238	61	28	18		219	19	63	62
VLA - MAT	0.02	0.25*	0.05	0.00 (0.20/0.19) ^1		0.00	0.08 (0.28/0.09) ^1	0.12	0.03
VLA - TS	0.13*	0.39**	0.44*	0.00 (0.00/0.13)		0.13	0.13 (0.30/0.04)	0.27	0.16
VLA - MAP	−0.10	−0.31*	−0.44*	−0.03 (0.00/–0.16)		−0.10*	−0.10 (–0.32/–0.08)	−0.25	−0.13
VLA - PS	0.13	0.37**	0.43*	0.22 (0.26/0.07)		0.10*	0.28 (0.28/0.24)	0.19	0.22
LA - MAP	0.31***	0.33*	0.66***	0.63** (0.46/0.44)		0.28***	0.80***(0.79***/0.37)	0.27*	0.42***
VLA - LA	−0.20**	−0.43**	−0.55**	−0.18 (–0.58*/–0.18)		−0.20**	−0.21 (–0.26/–0.49)	−0.17	−0.38**
Relative change in the strength of correlation
VLA - MAT	0.02	++	0	0 (+/+) ^1		0	+ (++/+) ^1	+	0
VLA - TS	0.13*	++	+++	– (–/0)		0	0 (+/-)	+	0
VLA - MAP	−0.10	++	+++	– (–/+)		0	0 (++/0)	+	0
VLA - PS	0.13	++	+++	+ (+/–)		0	+ (+/+)	+	+
LA - MAP	0.31***	0	+++	+++ (+/+)		0	+++ (+++/+)	0	+
VLA - LA	−0.20**	++	+++	0 (+++/0)		0	0 (+/++)	0	+

*** p < 0.001

** p < 0.01

* p < 0.05

¹ in parentheses λ = 0 / λ = 1.